AN MRI-based measurement may improve progressive supranuclear palsy (PSP) diagnosis, according to a secondary analysis of data from 2,111 participants. Researchers found that the dual-line midbrain PSP index (DMPI), a new linear MRI marker, accurately distinguished PSP from other neurodegenerative parkinsonian disorders.
PSP is a progressive neurodegenerative condition that affects movement, balance and eye movements. Distinguishing it from Parkinson disease, multiple system atrophy and corticobasal syndrome can be difficult, particularly during the early stages of disease, when symptoms may overlap.
Improving Progressive Supranuclear Palsy Diagnosis
The study evaluated whether established MRI measurements or a new linear marker could better differentiate PSP from other parkinsonisms. Investigators compared several previously reported MRI markers, including the midbrain line, midbrain area, pons-to-midbrain area ratio and MR parkinsonism index, with the DMPI, a new linear marker based on two midbrain measurements.
The analysis included participants with PSP, non-PSP parkinsonisms and healthy controls from international cohorts enrolled between 2006 and 2024. The training cohort consisted of Italian participants recruited at a single institution, the University of Catanzaro.
Strong Performance Across Multiple Cohorts
A total of 2,111 participants were included, with a mean age of 67.8 years; 54% were male. Researchers first compared all MRI markers in a representative sub-cohort comprising 161 participants with PSP and 203 with non-PSP parkinsonisms.
All evaluated measures achieved area under the receiver operating characteristic curve (AUC) values greater than 0.90 for differentiating PSP from other parkinsonian disorders. However, the DMPI delivered the highest performance, with an AUC of 0.97, while the midbrain area measurement achieved an AUC of 0.95.
The DMPI also produced the smallest proportion of uncertain classifications, with only 7.97% of cases falling within the diagnostic grey zone.
Potential Value in Early Disease
The DMPI maintained strong diagnostic accuracy in the larger Italian and international cohorts, achieving AUCs of 0.97 and 0.96, respectively. Notably, performance remained high among participants with early-stage disease, with an AUC of 0.97.
In a smaller cohort of 43 participants with pathologically confirmed diagnoses, the DMPI also demonstrated strong discrimination, achieving an AUC of 0.94.
Findings Need Further Clinical Validation
As a secondary analysis of existing prospective studies, the findings suggest that both the DMPI and midbrain area measurements could support the differential diagnosis of PSP. While the results indicate robust diagnostic performance across multiple cohorts, further work will be needed to determine how these MRI markers perform in routine clinical practice and whether they can help streamline diagnostic decision-making in patients presenting with parkinsonian syndromes.
Reference
Quattrone A et al. Planimetric and linear MRI markers for progressive supranuclear palsy classification: a large multicohort international study. Radiology. 2026;DOI:10.1148/radiol.251394.
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